9360

• UCREFRP Catalog Number: 9360
• Author: Bundy, J. M. and K. R. Bestgen.
• Title: Evaluation of the Interagency Standardized Monitoring program Sampling Technique in Backwaters of the Colorado River in the Grand Valley, Colorado.
• USFW Year: 2001.
• USFW - Doc Type: Fort. Collins.
• Copyright Material: NO

ISMP backwater sampling evaluation
DISCUSSION
The main goal of this study was to estimate bias and precision of the ISMP sampling
program to detect presence and estimate abundance of centrarchid fishes in backwaters of the
Colorado River. Overall, the ISMP sampling approach underestimated the number of backwaters
occupied by largemouth bass and green sunfish by about 50 %. In other words, ISMP detected
those centrarchid species in only every other backwater in which they occurred. When ISMP
sampling detected largemouth bass and green sunfish in Colorado River backwaters, abundance
of those taxa was underestimated compared to more reliable removal or capture-recapture
sampling. Details of analyses that led to these findings are discussed below. Although detection
and abundance estimation of centrarchids was not an original goal of ISMP sampling, managers
needed to understand whether this approach could be useful for such. The results of this study
suggest that a more intensive monitoring program needs to be developed to achieve the goal of
more accurate estimates of distribution and abundance of centrarchids in backwaters of the
Colorado River.
ISMP performance
The logistic regression analysis suggested that relatively large numbers of the target
centrarchid species needed to be present for ISMP sampling to simply detect the species with a
relatively modest probability of 0.5. The ISMP sampling technique sometimes failed to detect
centrarchids, especially largemouth bass, even when they were quite common (e.g., backwater #
' 4.2, Fig. 13).
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